This application contains subject matter related to a co-pending application Ser. No. 09/775,404 entitled xe2x80x9cA Method and Apparatus for Providing Continued Operation of a Multiprocessor Computer System after Detecting Impairment of a Processor Cooling Devicexe2x80x9d by Benjamin D. Osecky et al. This application is hereby incorporated by reference, is assigned to the same assignee as the present application, and was filed on Jan. 31, 2001, which is also the date on which the present application was filed.
The present invention relates to cooling fans in computer systems. More specifically, the present invention relates to detecting that a cooling fan is obstructed, and clearing the obstruction by manipulating the speed and direction of the cooling fan.
In the art of computing, it is desirable to maximize the availability of a computer system. This is known in the art as high availability (HA) computing. Companies desiring to market HA computing systems have set very high goals. For example, Hewlett-Packard Company has announced a goal of achieving 99.999% availability for high-end server platforms. This translates to about five minutes of downtime per year.
The design of an HA computer encompasses many of the computer""s subsystems. For example, redundant and uninterruptible power supples, error correcting memories, disk array subsystems, and robust software are all critical to the design of an HA computer system.
Even if it is not critical that a computer system have a high rate of availability (e.g., a desktop workstation), it is still desirable that the computer system be as robust as possible. Therefore, over time many methods and techniques that are originally deployed in HA computer systems become practical and cost-effective in other types of computer systems.
In most computer systems, cooling is an important function. Cooling is often provided by fans. A typical computer system may have one or more fans that draw air through the computer case and the power supply. In addition, small turbo cooler fans (which are also known as CPU fans) are often used to cool devices within the computer case, such as the central processing units (CPUs), motherboard chipset integrated circuits (ICs), or graphic device processors. One popular line of turbo cooler fans is the ArctiCooler family of turbo cooler fans, which are a product of Agilent Technologies, Inc. Of course, turbo cooler fans are also available from many other companies.
On problem associated with cooling fans is that is possible that an obstruction may block airflow through the fan. Consider, for example, what may happen if an operator temporarily places one or more sheets of paper on top of a computer system. A small draft could blow one of the sheets of paper toward the rear of the computer system, where the paper could be drawn toward an air intake of the system and obstruct the intake. Accordingly, the temperature within the computer system would begin to increase, and the computer system may fail. Other objects may also obstruct an air intake, such as leaves, insects, or dust.
It is also possible that a turbo cooler fan within the computer system case may become obstructed. For example, many computer systems have labels affixed to the inside of the computer case using an adhesive backing. Over time, the adhesive backing may fail, and the label may become detached. If the label were to be drawn into a turbo cooler fan and completely obstruct the fan, the temperature of the CPU would begin to rise and the CPU would fail. In addition, it is common to operate computer systems for extended periods of time with the case cover removed, in which case it is also possible that an external object, such as a sheet of paper or a leaf, could enter the case and obstruct the turbo cooler fan. To maximize the availability of any computer system that uses computer fans, it would be desirable if such an obstruction could be cleared using a simple and inexpensive method.
The present invention allows a computer system to attempt to remove a cooling fan obstruction by manipulating fan rotation. When the present invention detects that the fan is obstructed, the fan is stopped. If the obstruction is caused by an object that was drawn toward the fan intake, such as a sheet of paper, this operation may clear the obstruction. The fan may also be reversed to attempt to blow the obstruction clear of the fan. Thereafter, the fan is returned to normal operation and is monitored to determine whether the obstruction was removed. If the fan is still obstructed, these steps can be repeated. If the attempts to clear the obstruction are unsuccessful, then the computer system operator or management software can be signaled.
The present invention may be implemented with varying degrees of sophistication. In a very simple configuration, the present invention could be completely contained within a xe2x80x9csmart fanxe2x80x9d. Such a fan could include appropriate logic that would reverse the fan direction upon detecting a sudden increase in fan speed, with an audible alarm that alerts the operator of an obstruction that can not be cleared. Similarly, a power supply could incorporate the present invention to attempt to clear an obstruction from the air intake of the supply. These relatively simple implementations have the advantage of being able to be incorporated into existing computer designs with little additional design effort. Accordingly, these implementations increase system reliability and robustness at little additional cost.
Alternatively, more sophisticated implementations can be coupled with system firmware and/or the operating system. For example, in one implementation, the operating system can be signaled to provide an orderly shutdown in the event of a failed attempt to clear an obstruction, and can be signaled to alert an operator of a successful obstruction removal so that the obstructing object can be removed from the vicinity of the fan. Even more sophisticated implementations are possible, such as coupling the present invention with a system that provides continued operation of a multiprocessor computer system after detecting impairment of a processor cooling device.
The present invention is very simple and inexpensive to implement. However, the present invention is very effective at clearing certain types of fan obstructions, thereby increasing system reliability, robustness, and availability.